This invention relates to conveyors and more particularly to belt conveyors of the type hereinafter referred to as channel belt conveyors.
Essentially, a typical channel belt conveyor includes a flexible, elongated, endless belt entrained around two pulleys mounted on horizontal axes at opposite ends of a belt supporting bed. In one known prior art construction, a bed is secured between the vertical webs of two elongated, horizontally disposed, structural channels, the webs of the structural channels forming the sides of the conveyor while the belt lies flat on the bed. Elongated seals of belting material are fixed to the inside webs of the channels and extend downwardly, frictionally engaging the belt in an attempt to seal off the edges of the belt.
This form of channel belt conveyor has found a particular application in the handling of various forms of treated tobacco products, such as cut filler, strip, and the like, prior to its conversion into a consumer item. When cut filler, for example, is conveyed by such a conveyor it has been found, however, that the conveyed material contains an undesired amount of "shorts" and "dust". "Shorts" is the term applied in the trade to pieces of tobacco which are smaller than desired for commercial processing and consumer use purposes. "Dust" is the term applied to tobacco dust apparently formed from tobacco particles during handling.
It is believed that the "shorts" and "dust" are caused by degradation of the conveyed tobacco particles which rub against the seals or the conveyor sides formed by the channels. This sliding engagement tears the particles or simply abrades them and this action is believed to contribute significantly to the amount of "shorts" and "dust" in the conveyed load.
A further problem encountered with this form of conveyor is that the seals are not effective to seal off all tobacco. Tobacco particles tend to find their way under the seals to the edge of the belt where they impact or "lump" between the seal, the belt and the side of the conveyor. Additionally, tobacco particles find their way under the belt and impact between the belt and the bed of the conveyor.
The lumps of tobacco present a severe problem in that when they find their way back into the mainstream of conveyed product, they cause malfunctions in downstream treatment apparatus such as in the feed station of the making machine. Impaction of tobacco under the belt causes belt wearing and belt drag problems as will be more fully discussed below.
A still further problem with this type of conveyor is that of infestation. The conveyors must periodically be stopped in order to clean them of insects which find their way into the areas behind the seals.
In another prior art construction, side boards or flanges are attached to the bed along their lower edges at the belt sides and between the pulleys in order to bend edge portions of the belt upwardly to form the load bearing run of the belt into a "channel"-like configuration. In an alternate known prior art construction, more expensive belt supporting rollers are substituted for the side boards.
Conveyors of this type, in particular those having fixed side flanges, however, have the disadvantage, when used with tobacco products, that particles of the tobacco product tend to overflow or otherwise find their way between the belt and the flanges or beds and there accumulate and impact. As the belt continues to move, more and more tobacco particles work their way into these areas and impact, with the result that the belt is severely loaded by frictional forces caused by the impacted tobacco. As more tobacco is impacted, friction and resulting belt loading increase until an overload point is reached where the belt automatically stops or stalls. In an extreme case, the impacting may be so severe as to pull the belt apart or wear it prematurely to shreds. In the case of overloading or stalling, the driving motors must then be stopped and the whole conveyor must be cleaned. The impacted tobacco is removed and is discarded as useless waste.
As a consequence of the tobacco impaction and resultant belt loading problem, channel belt conveyors generally are now provided with substantially more horsepower output capability, for driving the belt, than normal design techniques would theoretically call for. The additional power is required in order that the conveyor might be operated, despite building accumulations of impacted tobacco, for an acceptable time between down time clean-ups. Aside from the expedient of increasing horsepower, the impaction-belt loading problem has been particularly vexing since the conveyor payload is usually a very light tobacco product weighing only several pounds per square foot of belt. Without the accumulation and impaction problem, less driving horsepower is required, yet no known solution has been proposed.
Insofar as tobacco handling is concerned then, the raised belt edge conveyor having flanges fixed to the belt supporting bed does not provide a problem-free alternative to the fixed sided-flat belt configuration first discussed above.
It has thus been one objective of this invention to provide a channel belt conveyor, of the type utilizing side flanges to lift edge portions of the belt, wherein belt loading by impaction of material particles under the belt is substantially reduced or eliminated.
It has also been desirable to provide some degree of versatility in a channel belt conveyor so that it can be used not only to handle limited varieties of tobacco, but to handle different forms of products, such as hands of tobacco, which do not require a channel belt conveyor but which could be handled on a flat belt conveyor.
It has thus been another objective of this invention to provide a channel belt conveyor having a plurality of uses including a conversion capability for handling varied products on a flat belt configuration.
In accordance with certain aspects of the present invention, a channel belt conveyor of the type having side flanges for raising edges of the belt is provided which substantially reduces the impaction of conveyed product between the belt and its supporting surfaces. A preferred embodiment of the invention includes a channel belt conveyor having a belt, a belt supporting bed, and belt edge supporting flanges removably mounted along the conveyor, each flange having a lower edge spaced form the bed and being adjustably mounted to vary the angle made between the supported belt edge portion and a central portion of the belt supported on the bed. Despite the particular inclination of the flange, its lower edge remains spaced from the bed to permit any foreign particles, which find their way between the belt and the flanges or bed, to work their way free of capture without impacting beneath the belt. Impaction and belt loading is thereby substantially reduced. Further, the flanges can be removed to permit the belt to lie flat when flat belt operation is necessary, as determined by the product to be conveyed.
In another aspect of the preferred embodiment of the invention, friction eliminating belt engaging rollers are removably mounted beneath the bed and extend upwardly therethrough to engage the belt just before belt engagement with the flanges. This reduces belt friction against the ends of the flanges as the belt is flexed from a relatively flat disposition to a channel-like configuration. Additionally, the rollers are uniquely adjustably mounted for disposition of the belt engaging roller surface in about the same angle of inclination as that of the flanges.
In still another aspect of a preferred embodiment of the invention, the bed of the conveyor extends outwardly of the flanges and then is directed downwardly to form the sides which vertically support the elongated conveyor, thereby providing a very economic one-piece structural component serving a dual function as both conveyor bed and conveyor support.
One of the primary advantages attained by the present invention is due to the substantial reduction of accumulated impacted tobacco and consequent reduction in belt loading. The necessary horsepower capability required to drive the belt can now be reduced by up to as much as 35% without detracting from the conveyor's operational efficiency. Further, the creation of "lumps" is eliminated and the creation of "shorts" and "dust" is reduced.